static variables and functions

What is the difference bet开发者_运维知识库ween instance and static variables/functions .Is there any performance gain using static variables.In which conditions we should use static instead of instance variables/functions. i'm not sure when I should use static variables/functions instead of instance ones

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Static members belong to the class, while instance members belong to instances (objects) of that class. There will only ever be one copy of a static variable.

Methods could be made static if:

1. They do not reference any non-static members of their class, and
2. They are not defined to implement an interface or override a method in a superclass.

Static methods do not have the hidden this parameter, so they require less stack space. But static methods are not inherently faster.

Fields/properties should only be made static if you only want one "copy" of the field/property. If you want each object of your class to have its own copy of a field or property, it should not be static.